package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value));
    }

    //缓存穿透--缓存空对象
    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        //1.从redistribution查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(keyPrefix + id);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(json, Shop.class);
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        // (null就是内存中根本没有这个东西，空字符串就是内存中有，但是值是空)
        //  null是没有数据，而我们存入的空值""
        if (json != null) {
            //返回一个错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //将空值写入redis--CACHE_NULL_TTL
            stringRedisTemplate.opsForValue().set(keyPrefix + id, "", (long) (Math.random() * 10 + 1), TimeUnit.MINUTES);
            return null;
        }
        //6.存在，写入redis
        this.set(keyPrefix + id, r, time, unit);
        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallBack,Long time,TimeUnit unit){
        String key = keyPrefix + id;
        //1.从Redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)){
            //3.不存在，返回空
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        //5.判断是否过期
        //5.1 未过期直接返回店铺信息
        LocalDateTime expireTime = redisData.getExpireTime();
        if(expireTime.isAfter(LocalDateTime.now())){
            return r;
        }
        //5.2 已过期重建缓存
        //6.缓存重建
        //6.1.获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2.判断是否获取互斥锁成功
        if(isLock){
            //6.3.成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallBack.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unlock(lockKey);
                }
            });

        }
        //6.4.失败，返回过期的商铺信息
        return r;
    }


    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }
}
